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From: Jelte Fennema-Nio <postgres@jeltef.nl>
Date: Fri, 5 Dec 2025 15:32:32 +0100
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Subject: Re: Safer hash table initialization macro
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
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On Fri, 5 Dec 2025 at 02:30, Thomas Munro <thomas.munro@gmail.com> wrote:
> How much of our header stuff is supposed to work from C++ too?

I think it's nice if it works, but it doesn't seem the most important.
Especially since C++ has its own hashmaps. And if it really needs to
create a hashmap it's still possible to call the.

> I suppose you could
> write the typeof-based version you already hinted at, but only use it
> for __cplusplus__ (where typeof exists as decltype).

I tried to figure something out that would work in C++ (with help of
Claude), but I wasn't able to create a version of the macros without
also needing to add:

#ifdef __cplusplus
}
#include <type_traits>
extern "C" {
#endif

It seems quite ugly to escape the extern "C" from the parent like that
and then re-enter it. Overall it doesn't seem worth the hassle to me
to make these macros work in C++.

> Another consideration is what impact we have on the Rust world, and
> potentially other languages used for extensions that call C via FFI
> etc

FFI generally cannot call macros anyway, only actual symbols.